Do you hold your farts in all day? My SO does, and when she goes to bed a few minutes before me, she will toot like the brass section of a big band sometimes. Practice letting them out silently during the day instead, all that gas has to go somewhere, you can't just hold it in

gas, trapped in the bowels when sitting or standing upright, is given an avenue of escape once the body lies prone

How long before bed do you eat? And what kind of foods do you eat? Have you tried using the washroom before bed?

Loosen your anus with a dildo each night so the farts can be silent.

It’s not just random that you roll over and then fart. You have uncomfortable gas buildup and when your body feels uncomfortable you shift positions. In this case your body is succeeding in finding the right position to relieve the pressure, via farting.

Gas is a nuisance but sleep disruption is a serious health risk. It will reduce your quality of life and cognitive performance in every measurable way and shorten your life.

So it’s time to address the root cause: the gas. It is not inevitable to have extreme gas. But you are going to have to do some work and accept some changes if you want to fix it. The easiest thing you can do is modify when you eat. Stop eating after 5pm each night and see what happens. Delay your dinner until 8pm and see what happens.

If you cannot find better timing then you must look at what you are eating. Eliminate beans/lentils and see what happens. Eliminate brassica vegetables (broccoli, brussel sprouts, cauliflower) and see what happens. Then cabbage. If none of that helps then look at eliminating carbs after 12 noon. See what happens.

May your farts and sleep improve.

Probably has to do with your body relaxing, similar to how dead people are prone to shitting themselves.

Just a guess tho I'm not a medical expert.

Might be a bit random, and perhaps a bit far fetched, but are you able to burp?

I've been struggling with the same thing for most of my life and was diagnosed with R-CPD ( retrograde cricopharygeal dysfunction a couple of months ago. Fortunately there is a treatment that is as good as 100% effective for this diagnosis.

(No burping = excessive flatulence)

Walking will help sort your guts out as well, so by going for a late walk, you can take the problem to the outside!

Otherwise it's probably just a question of your gut biome having a lot of gas producing parts.

As you relax, so do your sphincter muscles.

That last line was the funniest thing I've read in the past few days, so thank you for that.

Sleeping on my side makes me fart so I sleep in my back to save my marriage

Do you know why you fart? Are you secretly lactose intolerant but don't know it?

Stop drinking milk.

Look at a low fodmap diet.

I don’t have any allergies or similar things that could be causing this as far as I know.

Are there allergies that cause excessive flatulence?

Probably diet. If u eat a lot of legumes or have very little fibre then that could probably be doing it.

Do you eat a lot of garlic? That's what gets me.

Farting as you relax and when you bring your knees up towards your chest (common when you sleep on your side) is pretty normal. It might also be a timing thing based on when you go to bed relative to when you've eaten.

You might look into why you fart so much if it's excessive. For instance, I have an odd food intolerance called fructose malabsorption - excess fructose doesn't get digested, so it just ferments in my intestines. If I eat a lot of it, I'll get massively painful diarrhea, but usually I just get some gas.

The same thing happens with people who are lactose intolerant: they can usually have some amount of lactose and they just get gassy, so some people don't even realize they have it.

Other things can also cause unusual amounts of gas.

When you say granola, is that bars or cereal with milk? You might have lactose intolerance building up if it's the latter.

Obligatory: I am not a doctor, I don't know your life.

Jumping off the other comment suggesting a low-fodmap diet, do you have other health problems? What sounds like an extremely unbalanced diet (possibility in combination with a round of antibiotics or an episode of food poisoning) may have resulted in a condition called SIBO (small intestine bacterial overgrowth), specifically an overgrowth of methane-producing bacteria. I'd recommend getting tested.